Yes, screen tops can filter out up to 50% of the UVB. Why not mount your UVB fixture inside the tank? There are a lot of ways of accomplishing that. If you tell me what kind of enclosure you have and what kind of fixture you're using, I should be able to help you out.
As for jumping, it depends on the beardie. My little baby beardie can jump really high because he only weighs 17 grams. My 8-month-old probably couldn't jump more than about 4 inches, because he weighs 350 grams. The baby is like a cricket... super fast and light. The older one is like a sloth... fat and slow.